^{115}In^{+}-^{172}Yb^{+} Coulomb Crystal Clock with 2.5×10^{-18} Systematic Uncertainty.

Area of Science:

• Atomic Physics
• Quantum Metrology
• Optical Clocks

Background:

• Atomic clocks are crucial for fundamental physics tests and timekeeping.
• Previous clocks faced limitations in accuracy and stability.
• Mixed-species ion crystals offer a promising approach to overcome these limitations.

Purpose of the Study:

• To present a scalable mixed-species Coulomb crystal atomic clock.
• To utilize the ^{1}S_{0}↔^{3}P_{0} transition in ^{115}In^{+} for clock operation.
• To achieve high precision in frequency measurements and comparisons.

Main Methods:

• Cotrapping ^{115}In^{+} and ^{172}Yb^{+} ions in a Coulomb crystal.
• Employing sympathetic cooling with ^{172}Yb^{+} ions.
• Using a conditional preparation sequence with permutation control for reproducible interrogation.

Main Results:

• Demonstrated clock operation with a 1In^{+}-3Yb^{+} crystal, achieving a relative systematic uncertainty of 2.5×10^{-18}.
• Reported absolute frequency measurements with an uncertainty of 1.3×10^{-16}.
• Achieved the most accurate frequency ratio measurement to date between ^{115}In^{+} and ^{171}Yb^{+} (E3) clocks with a fractional uncertainty of 4.4×10^{-18}.

Conclusions:

• The mixed-species Coulomb crystal clock offers a scalable platform for high-precision timekeeping.
• This work significantly improves frequency ratio measurements, particularly for ^{115}In^{+}/^{87}Sr.
• The developed clock technology paves the way for future advancements in metrology and fundamental science.